C#: Simplify implementation.

Author: michaelnebel

csharp/ql/lib/semmle/code/csharp/Assignable.qll

@@ -292,8 +292,7 @@ module AssignableInternal {
     newtype TAssignableDefinition =
       TAssignmentDefinition(Assignment a) {
         not a.getLValue() instanceof TupleExpr and
-        not a instanceof AssignCompoundOperation and
-        not a instanceof AssignCoalesceExpr
+        (not a instanceof AssignOperation or a instanceof AddOrRemoveEventExpr)
       } or
       TTupleAssignmentDefinition(AssignExpr ae, Expr leaf) { tupleAssignmentDefinition(ae, leaf) } or
       TOutRefDefinition(AssignableAccess aa) {
@@ -318,10 +317,7 @@ module AssignableInternal {
       } or
       TAddressOfDefinition(AddressOfExpr aoe) or
       TPatternDefinition(TopLevelPatternDecl tlpd) or
-      TAssignOperationDefinition(AssignOperation ao) {
-        ao instanceof AssignCompoundOperation or
-        ao instanceof AssignCoalesceExpr
-      }
+      TAssignOperationDefinition(AssignOperation ao) { not ao instanceof AddOrRemoveEventExpr }
 
     /**
      * Gets the source expression assigned in tuple definition `def`, if any.

csharp/ql/lib/semmle/code/csharp/commons/Strings.qll

@@ -49,14 +49,9 @@ class ImplicitToStringExpr extends Expr {
       this = add.getOtherOperand(o).stripImplicit()
     )
     or
-    // s1 += s2 for where the left hand side is a string, call an operator +(string, object)
-    exists(AssignAddExpr add, Operator o, Parameter p0, Parameter p1 |
-      o = add.getTarget() and
-      o.getName() = "+" and
-      p0 = o.getParameter(0) and
-      p1 = o.getParameter(1) and
-      p0.getType() instanceof StringType and
-      this = getAnAssignedArgumentOrParam(p1).stripImplicit()
+    exists(AssignAddExpr add, Expr o | o = add.getLeftOperand() |
+      o.stripImplicit().getType() instanceof StringType and
+      this = add.getRightOperand().stripImplicit()
     )
     or
     this = any(InterpolatedStringExpr ise).getAnInsert().stripImplicit()

csharp/ql/lib/semmle/code/csharp/dispatch/Dispatch.qll

@@ -202,7 +202,7 @@ private module Internal {
   private predicate isPotentialEventCall(
     AssignArithmeticOperation aao, DynamicMemberAccess dma, string name
   ) {
-    aao instanceof DynamicOperatorCall and
+    aao instanceof DynamicAssignOperation and
     dma = aao.getLeftOperand() and
     (
       aao instanceof AssignAddExpr and

csharp/ql/lib/semmle/code/csharp/exprs/Assignment.qll

@@ -60,10 +60,11 @@ class AssignExpr extends Assignment, @simple_assign_expr {
 
 /**
  * An assignment operation. Either an arithmetic assignment operation
- * (`AssignArithmeticOperation`), a bitwise assignment operation or
- * (`AssignBitwiseOperation`).
+ * (`AssignArithmeticOperation`), a bitwise assignment operation
+ * (`AssignBitwiseOperation`), an event assignment (`AddOrRemoveEventExpr`)
+ * or a null-coalescing assignment (`AssignCoalesceExpr`).
  */
-class AssignOperation extends Assignment, @assign_op_expr {
+class AssignOperation extends Assignment, LateBindableExpr, @assign_op_expr {
   override string getOperator() { none() }
 
   /**
@@ -79,11 +80,9 @@ class AssignOperation extends Assignment, @assign_op_expr {
   override string toString() { result = "... " + this.getOperator() + " ..." }
 }
 
-/**
- * An assignment operation that corresponds to an operator call, for example `x += y` corresponds to `x = x + y`.
- */
-class AssignCompoundOperation extends AssignOperation, OperatorCall, @assign_op_call_expr {
-  override string toString() { result = "... " + this.getOperator() + " ..." }
+/** An assignment operation involving a dynamic operator call. */
+class DynamicAssignOperation extends DynamicExpr, AssignOperation {
+  override string toString() { result = "... dynamic " + this.getOperator() + " ..." }
 }
 
 /**
@@ -93,7 +92,7 @@ class AssignCompoundOperation extends AssignOperation, OperatorCall, @assign_op_
  * operation (`AssignDivExpr`), or a remainder assignment operation
  * (`AssignRemExpr`).
  */
-class AssignArithmeticOperation extends AssignCompoundOperation, @assign_arith_expr { }
+class AssignArithmeticOperation extends AssignOperation, @assign_arith_expr { }
 
 /**
  * An addition assignment operation, for example `x += y`.
@@ -149,7 +148,7 @@ class AssignRemExpr extends AssignArithmeticOperation, @assign_rem_expr {
  * operation (`AssignRightShiftExpr`), or an unsigned right-shift assignment
  * operation (`AssignUnsignedRightShiftExpr`).
  */
-class AssignBitwiseOperation extends AssignCompoundOperation, @assign_bitwise_expr { }
+class AssignBitwiseOperation extends AssignOperation, @assign_bitwise_expr { }
 
 /**
  * A bitwise-and assignment operation, for example `x &= y`.

csharp/ql/lib/semmle/code/csharp/exprs/Call.qll

@@ -493,7 +493,7 @@ class ConstructorInitializer extends Call, @constructor_init_expr {
  * }
  * ```
  */
-class OperatorCall extends Call, LateBindableExpr, @op_invoke_expr {
+class OperatorCall extends Call, LateBindableExpr, @operator_invocation_expr {
   override Operator getTarget() { expr_call(this, result) }
 
   override Operator getARuntimeTarget() { result = Call.super.getARuntimeTarget() }

csharp/ql/lib/semmle/code/csharp/exprs/Dynamic.qll

@@ -12,7 +12,8 @@ private import semmle.code.csharp.dispatch.Dispatch
  * dynamic constructor call (`DynamicObjectCreation`), a dynamic method call
  * (`DynamicMethodCall`), a dynamic operator call (`DynamicOperatorCall`), a
  * dynamic member access (`DynamicMemberAccess`), a dynamic accessor call
- * (`DynamicAccessorCall`), or a dynamic element access (`DynamicElementAccess`).
+ * (`DynamicAccessorCall`), a dynamic element access (`DynamicElementAccess`),
+ * or a dynamic assignment operation (`DynamicAssignOperation`).
  */
 class DynamicExpr extends LateBindableExpr {
   DynamicExpr() { this.isLateBound() }

csharp/ql/lib/semmle/code/csharp/exprs/Expr.qll

@@ -118,8 +118,8 @@ class Expr extends ControlFlowElement, @expr {
  * An expression whose target may be late bound when using `dynamic`
  * subexpressions. Either a method call (`MethodCall`), an operator call
  * (`OperatorCall`), a constructor call (`ObjectCreation`), a dynamic member
- * access (`DynamicMemberAccess`), or a dynamic element access
- * (`DynamicElementAccess`).
+ * access (`DynamicMemberAccess`), a dynamic element access
+ * (`DynamicElementAccess`), or an assignment operation (`AssignOperation`).
  */
 class LateBindableExpr extends Expr, @late_bindable_expr {
   /** Holds if this expression is late bound. */

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -1216,8 +1216,7 @@ case @expr.kind of
               | @string_literal_expr | @null_literal_expr;
 
 @assign_expr = @simple_assign_expr | @assign_op_expr | @local_var_decl_expr;
-@assign_op_call_expr = @assign_arith_expr | @assign_bitwise_expr
-@assign_op_expr =  @assign_op_call_expr | @assign_event_expr | @assign_coalesce_expr;
+@assign_op_expr =  @assign_arith_expr | @assign_bitwise_expr | @assign_event_expr | @assign_coalesce_expr;
 @assign_event_expr = @add_event_expr | @remove_event_expr;
 
 @assign_arith_expr = @assign_add_expr | @assign_sub_expr | @assign_mul_expr | @assign_div_expr
@@ -1271,15 +1270,14 @@ case @expr.kind of
 
 @anonymous_function_expr = @lambda_expr | @anonymous_method_expr;
 
-@op_invoke_expr = @operator_invocation_expr | @assign_op_call_expr
-@call = @method_invocation_expr | @constructor_init_expr | @op_invoke_expr
+@call = @method_invocation_expr | @constructor_init_expr | @operator_invocation_expr
       | @delegate_invocation_expr | @object_creation_expr | @call_access_expr
       | @local_function_invocation_expr | @function_pointer_invocation_expr;
 
 @call_access_expr = @property_access_expr | @event_access_expr | @indexer_access_expr;
 
 @late_bindable_expr = @dynamic_element_access_expr | @dynamic_member_access_expr
-                    | @object_creation_expr | @method_invocation_expr | @op_invoke_expr;
+                    | @object_creation_expr | @method_invocation_expr | @operator_invocation_expr | @assign_op_expr;
 
 @throw_element = @throw_expr | @throw_stmt;